Thermal cycling tests were performed to check the stability in thermal energy storage systems on some selected organic and inorganic phase change materials (PCMs). The possibility of using these PCMs in thermal energy storage systems were examined on the basis of thermal, chemical and kinetic criteria. Organic and inorganic PCMs were selected to check their thermal stability. Inorganic PCMs were not found suitable after some cycles while thermal cycling for organic PCMs were undertaken up to 1000 thermal cycles and has shown a gradual change in melting temperature and latent heat of fusion. The PCMs were then checked with differential scanning calorimeter (DSC) for their latent heat storage capacity and melting temperature change. (c) 2008 Elsevier Ltd. All rights reserved.